A porous conducting polymer/heteropolyoxometalate hybrid material that displays high specific capacitance and low ionic resistance has been prepared for electrochemical supercapacitor applications. Polypyrrole/phosphomolybdate composite films were chemically synthesized in tetrahydrofuran in the presence of sodium sulfate, which acts as a porogen. While the phosphomolydic acid could be removed from the film upon rinsing with pure tetrahydrofuran or acetone, rinsing with water or methanol resulted in retention of the heteropolyoxometalate at a level high enough to easily observe its electrochemistry. The retained phosphomolybdate exhibits fast and reversible redox behavior, adding a significant amount of pseudocapacitance to the polymer. Porous films were obtained by leaching out the sodium sulfate porogen from the films using water. The morphology obtained using this method is altered by varying the monomer-to-porogen ratio. Increasing the porosity increases the rate at which the hybrid material can be charged/discharged (i.e., oxidized/reduced) by increasing the ionic conductivity and in turn lowering the resistor-capacitor time constant of the material. The ability to tune the porosity of the material allows the optimization of performance characteristics for use in supercapacitor applications. Impedance measurements indicate that the ionic conductivity of these porous structures can be increased more than an order of magnitude over that observed for standard conducting polymer films and that the hybrid material displays peak specific capacitance of around 700 F/g as well as excellent reversibility and cyclability.

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An asymmetric conducting polymer/polyoxometalate ͑POM͒ supercapacitor was designed using polypyrrole/phosphomolybdic acid and poly͑3,4-ethylenedioxythiophene͒/phosphotungstic acid as electrode materials. Performance characteristics were measured by cyclic voltammetry and constant current discharge. Energy density and power density were increased by a factor of 3 and 50, respectively, over symmetric conducting polymer/POM systems.

In this report, we examine the origin of photocurrent produced by irradiating single layer poly(3-hexylthiophene) (P3HT) films deposited on ITO-coated glass, in aqueous solutions. The photocurrent is found to be largely due to reduction of trace molecular oxygen, which decreases significantly in the presence of an oxygen scavenger. Residual current, < 1 μA cm −2 , is observed in acidic media that may be attributed to proton reduction. The addition of a catalyst to aid proton reduction is achieved through photoelectrochemical deposition of Pt nanoparticles from K 2 PtCl 6 . Photocurrents at single layer films in aqueous solution increase significantly and bubble formation is observed on the P3HT film that is confirmed to be hydrogen gas. While the photocurrents produced are smaller than those devices employing sophisticated multilayer architectures, the results hold promise that, with further studies, H 2 can be evolved at technologically-simple single layer systems with substantially higher rates.Photoelectrochemistry (PEC) of redox species in aqueous solutions has undergone a resurgence of interest due to a desire to develop inexpensive, renewable fuels. In the seminal work of Fujishima and Honda, oxygen and hydrogen gas were produced upon the photoassisted electrolysis of water at an illuminated n-type TiO 2 electrode and Pt black counter electrode. 1 PEC of n-type TiO 2 has two main drawbacks. The first is that, whereas, photo-generated "holes" arising from the valence band are sufficiently energetic (thermodynamically) to oxidize water to oxygen gas, conduction band electrons are insufficiently energetic to reduce water to hydrogen gas, hence the requirement to negatively bias the counter electrode. The second drawback is that TiO 2 absorbs a relatively small fraction of the solar spectrum due to its large bandgap (∼3 eV); the "solar" efficiencies obtained are, therefore, relatively low. As a consequence, research effort is being directed to the study of other inorganic semiconductors including alternative metal oxides, 2-5 silicon and other compound semiconductors, 6-9 and composites of the two, 10-12 with the intention of enhancing photoelectrochemical water splitting reaction kinetics and solar-to-fuel efficiencies.An alternate strategy to employing a single semiconductor to generate electrons and holes that simultaneously split water photoelectrochemically is to design individual n-and p-type semiconductors with the specific task of oxidizing and reducing water that evolve oxygen at photoanodes and hydrogen at photocathodes 13,14 or from tandem semiconductor devices. 15,16 Another approach fosters consideration of materials other than metal oxides and inorganic semiconductors. [17][18][19][20][21] Organic semiconducting polymers would appear prime candidates for photocathode materials because they absorb visible light, are typically p-type, meaning that during illumination electrons flow toward the electrode surface, and they participate actively in electron transfer reactions. Optoelectronic studies of p...